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.\" This manpage is copyright (C) 1992 Drew Eckhardt,
.\"                 copyright (C) 1995 Michael Shields.
.\"
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.\" which is licensed free of charge, as they might when working
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.\" Formatted or processed versions of this manual, if unaccompanied by
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.\" Modified 1993-07-24 by Rik Faith <faith@cs.unc.edu>
.\" Modified 1995-05-18 by Jim Van Zandt <jrv@vanzandt.mv.com>
.\" Sun Feb 11 14:07:00 MET 1996  Martin Schulze  <joey@linux.de>
.\"	* layout slightly modified
.\"
.\" Modified Mon Oct 21 23:05:29 EDT 1996 by Eric S. Raymond <esr@thyrsus.com>
.\"
.\" Japanese Version Copyright (c) 1997 HANATAKA Shinya
.\"         all rights reserved.
.\" Translated Sun Feb 23 22:43:33 JST 1997
.\"         by HANATAKA Shinya <hanataka@abyss.rim.or.jp>
.\" Modified Mon May  5 19:44:46 JST 1997
.\"         by HANATAKA Shinya <hanataka@abyss.rim.or.jp>
.\"
.\"WORD:	synchronous		Ʊ
.\"WORD:	multiplexing		¿Ų
.\"WORD:	descriptor		ǥץ
.\"WORD:	macro			ޥ
.\"WORD:	block			(block)
.\"WORD:	block			ػ(block)
.\"WORD:	signal			ʥ
.\"WORD:	timeout			ڤ(timeout)
.\"WORD:	portable		ܿΤ
.\"
.TH SELECT 2 "February 11, 1996" "Linux 1.2" "Linux Programmer's Manual"
.SH ̾
select, FD_CLR, FD_ISSET, FD_SET, FD_ZERO \- ¿Ų줿 I/O ƱȤ
.SH 
.B #include <sys/time.h>
.br
.B #include <sys/types.h>
.br
.B #include <unistd.h>
.sp
\fBint select(int \fIn\fB, fd_set *\fIreadfds\fB,
fd_set *\fIwritefds\fB, fd_set *\fIexceptfds\fB,
struct timeval *\fItimeout\fB);
.sp
.BI "FD_CLR(int " fd ", fd_set *" set );
.br
.BI "FD_ISSET(int " fd ", fd_set *" set );
.br
.BI "FD_SET(int " fd ", fd_set *" set );
.br
.BI "FD_ZERO(fd_set *" set );
.fi
.SH 
.B select
ϤĤΥե롦ǥץ(file descriptor)ξ֤
ѲΤԤġ
.PP
ĤΩǥץνƻ뤹롣
.I readfds
˥ꥹȤ줿Τɤ߹ߤǽɤƻ뤹롣
.I writefds
˥ꥹȤ줿ΤϤˤ˽񤭹ߤǽɤƻ뤹롣
.I exceptfds
ˤΤ㳰δƻԤʤλˡºݤˤɤ
ǥץξ֤Ѳ˽礬ѹ롣
.PP
뤿˻ͤĤΥޥ(macro)󶡤롣
.B FD_ZERO
Ͻõ(clear)롣
.B FD_SET

.B FD_CLR
Ͻ˥ǥץäꤹ롣
.B FD_ISSET
Ͻ˥ǥץ뤫ɤĴ٤; 
.B select
λǤ롣
.PP
.I n
ϻĤνˤǥץκͤ 1 ­Ρ
.PP
.I timeout

.B select
֤äƤޤǤηв֤ξ¡ϥˤ뤳ȤǤ
ξ
.B select
Ϥ֤äƤ롣⤷
.I timeout
 NULL (ڤ(timeout)̵)
ꤵȡ
.B select
̵¤(block)롣
.SH ֤
硢
.B select 
ϥǥץ˴ޤޤƤǥ꥿ο֤
ζ̣ݤ˻ڤˤʤäϥˤʤ뤳Ȥ⤢롣
顼ʤ -1 ֤
.I errno
Ŭڤͤꤵ; 
.I timeout
̤Ȥʤ롢顼θϤƤϿǤʤ
.SH 顼
.TP
.B EBADF
Τɤ줫̵ʥեǥץͿ줿
.TP
.B EINTR 
ػ(block)Ƥʤʥ(signal)
.TP
.B EINVAL 
.I n
Ǥ롣
.TP
.B ENOMEM
.B select
ơ֥˥꡼Ƥ뤳ȤǤʤä
.SH 
.B select
ƤӽФɤˤϻĤνƤ˶ꤷ
.I n
˥
.I timeout
 NULL Ǥʤͤꤷܿ(portable)Τˡñ̰ʲ
꡼(sleep)¸ƤΤ롣
.PP
Linux Ǥϡ
.I timeout
(sleep)Ƥʤ֤̤ȿǤ褦˽줿
¾ΤۤȤɤΥץơǤϤΤ褦ˤʤäƤʤ

.I timeout
ɤ߼ Linux Υɤ¾Υڥ졼ƥ󥰡ƥذܿ
 롼פ timval ¤Τ˺ƻѤʣ 
.BR select
ԤʤäƤ륳ɤ Linux ذܿξ򵯤
.B select
֤äƤ
.I timeout
̤Ǥȹͤ٤Ǥ롣
.SH 
.nf
#include <stdio.h>
#include <sys/time.h>
#include <sys/types.h>
#include <unistd.h>

int
main(void)
{
    fd_set rfds;
    struct timeval tv;
    int retval;

    /* Watch stdin (fd 0) to see when it has input. */
    FD_ZERO(&rfds);
    FD_SET(0, &rfds);
    /* Wait up to five seconds. */
    tv.tv_sec = 5;
    tv.tv_usec = 0;

    retval = select(1, &rfds, NULL, NULL, &tv);
    /* Don't rely on the value of tv now! */

    if (retval)
        printf("Data is available now.\\n");
        /* FD_ISSET(0, &rfds) will be true. */
    else
        printf("No data within five seconds.\\n");

    exit(0);
}
.fi

.SH 
4.4BSD (
.B select
ؿ 4.2BSD Ǻǽ˸줿) ̤ BSD Υåؤ򥵥ݡȤ
BSD ʳΥƥ(System V Ѽޤ)ؤΰܿޤϤ줫ΰܿ
Ǥ롣 System V ѼŵŪ timeout ѿꤹ
ΤФơBSDѼǤꤷʤȤդ뤳ȡ
.SH Ϣ
.BR accept (2),
.BR connect (2),
.BR poll (2),
.BR read (2),
.BR recv (2),
.BR send (2),
.BR write (2)